In the United States, approximately 80% of hospital patients require intravenous (IV) therapy and approximately 50% of the IV lines fail due to infiltration, a clot in the cannula, an inflammatory response of the vein, or separation of the cannula from the vein. IV infiltration is usually accompanied by pain, erythema, and/or swelling at the cannula tip or the insertion site. Severe infiltration may lead to necrosis requiring skin debridement, skin grafting, or amputation. One common area of malpractice lawsuits filed against physicians and nurses involves infiltration. The leakage of cytotoxic drugs, intravenous nutrition, solutions of calcium, potassium, and bicarbonate, and even 10% dextrose outside the vein into which they are delivered is known to cause tissue necrosis and to precipitate significant scarring around joints. An infiltration rate of 0.1-1% has been reported in cases where contrast agents were used in medical imaging procedures. Early detection of infiltration prevents the occurrence of serious incidents that may require surgical correction.
It has been postulated that there are six predictors of infiltration—catheter material, age of patients, anatomic insertion site, hyperalimentation, the use of furosemide, and the use of dopamine. The age of patient is a very important factor for the risk of infiltration. Because the amount of connective tissue is limited in elderly patients as well as the very young, they are prone to extensive diffusion of infiltrated fluid. The patient's osmotic balance is another important consideration. Obese patients or patients with low albumin or edema may not have normal tissue responses to pressure.
Infiltration may develop in different ways: (a) the steel needle or plastic cannula may pierce the wall of the vein, allowing fluid to flow into the interstitial space; (b) a clot distal to the cannula may develop, causing narrowing of the vein wall, blocking blood flow, increasing backpressure, and infiltration at the needle insertion site; (c) certain IV fluids may cause change in blood pH and constriction of veins with increasing pressure and subsequent infiltration; (d) the IV cannula or the infused solution may cause an inflammatory reaction, increasing permeability of the vein and allowing fluid to leak into surrounding tissues; and (e) the cannula may be dislodged from the vein. The extent of tissue damage caused by infiltration depends on the drug, the dosage, the site of IV administration, and the exposure duration. Injuries due to infiltration of cytotoxic drug infusions range from 0.1-0.7%. Severe infiltration injuries often require surgical treatment and even amputation. One study reported that infiltration results in skin loss in 0.24% of the peripheral lines.
There are several methods currently existing for detecting infiltration: visual and tactile examinations; monitoring IV line pressure; checking for blood return; and electromagnetic radiation detection.
Visual and tactile examinations of IV sites are the most widely used methods for detecting infiltrations. The infiltrated site may appear swollen or puffy. In this case erythema may also be present. Infiltrations may also appear as a pale area where the infiltrate has pooled below the skin. The skin may feel cooler than the surrounding area due to rapid entrance of the IV fluid into the tissue before it can be warmed to body temperature. The visual and tactile examination technique is ineffective in detecting infiltration, since by the time infiltration is detected, tissue damage has already occurred.
IVs are administered either by gravity control or infusion pumps. For gravity control, the solution head height, defined as the vertical distance from the fluid meniscus to the IV site, generates the pressure necessary to infuse IV fluid. In theory, gravity control would stop fluid infusion when sufficient fluid accumulates in the interstitial space. Once the fluid flow stops, an alarm alerts the nurse to check the IV site. For gravity control IV, the solution reservoir can be lowered to below IV sites. If blood flows toward the lowered reservoir, infiltration is less likely to occur. However, this technique cannot reliably detect infiltration.
Infusion pumps provide volumetric and timed delivery of IV fluids under conditions of increased resistance to flow. The occlusion pressure can be as high as 25 psi (1293 mm Hg). The disadvantage of maintaining a high pressure is that a potential hazard to patients exists should infiltration occur. Studies of the performance of low, non-variable pressure infusion pumps in alerting the nurses to infiltrations, show that while 64% of IV sites show clinical evidence of infiltration, no alarm occurs. It has been reported that infiltration may be detected by monitoring the IV pressure, one measures either the in-line IV pressure or the in-line IV pressure dissipation after a brief pressure increase. However, both pressure monitoring methods have proven unreliable, since there is limited predictability of change in in-line pressure following infiltration. Perfusion, diffusion, and metabolic processes occurring in living tissue and intra- and inter-patient differences render the use of pressure monitoring for infiltration detection ineffective.
Another method of checking for infiltration is to look for a blood return. Removing the positive pressure caused by the infusion controller (either gravity or infusion pump) checks for the presence of a blood return. While the lack of a blood return indicates infiltration, the presence of a blood return cannot be construed as the absence of an infiltration.
One commercial device, the Venoscope® uses transillumination to locate the patient's peripheral venous network. It employs two movable optical fibers to illuminate the skin. The veins appear as dark areas beneath the skin. Detection of veins is by visual inspections. The Venoscope® must be used in a dimly lit room in order to have sufficient contrast to locate the venous network. It has been claimed that the Venoscope® can be used to detect IV infiltration. However, the detection is performed by subjective visual inspections.
Another method of detecting infiltration is described in U.S. Pat. No. 4,877,034 (Atkins). The Atkins invention teaches an IV monitoring technique that allows detection of tissue infiltration by exposing tissue surrounding the site of intravenous injection to a plurality of wavelengths of electromagnetic radiation. Changes in the relative levels of the detected radiation at each wavelength as compared to a baseline reading obtained when no infiltration is occurring indicate tissue infiltration. Electromagnetic radiation sources of at least two different wavelengths of radiation are used to direct electromagnetic radiation at the tissue surrounding the intravenous insertion site. The amount of radiation reflected, scattered and absorbed under certain conditions depends on the wavelength of the electromagnetic radiation and local tissue properties. The intensities of the detected radiation at the two wavelengths change when infiltration occurs, and these changes are different for different wavelengths. That is, infiltration affects the intensity of the detected electromagnetic radiation at one wavelength more than that of the second wavelength, allowing the difference to be used to indicate infiltration. While Atkins teaches a noninvasive method of detecting tissue infiltration, it is unnecessarily complex.
U.S. Pat. No. 6,487,428 (Culver) describes an IV monitoring apparatus for detecting IV infiltration by monitoring light transmitted through the tissue of the patient in proximity to a site at which fluid is being injected. Light is irradiated from a plurality of light sources in an encoded manner into the body part at the site at which the fluid is injected and the light that is reflected, scattered, diffused or otherwise emitted from the body part is detected individually by a plurality of light detectors. Signals representative of the detected light are collected and, prior to injection of the fluid, references are developed against which measurements made during injection of the fluid are compared. Like Atkins, the Culver invention is unnecessarily complex.
To solve the shortcomings in the existing systems, a need exists for a simple, reliable, inexpensive, and noninvasive method of monitoring IV sites for early detection of infiltration.